Construction of retractable landing gear



March so, 1948. SAULMER 2,438,650

CONSTRUCTION OF RETRACTABLE LANDING GEARS Filed Feb. 15, 1942 h 2Sheets-Sheet l In uezzt v j? S a, u lzzaez' March 30, 1948. R. SAULNIERCONSTRUCTION OF RETRACTABLE LANDING ,,GEARS 2 Sheets-Sheet 2 Filed Feb..13, 1942 Inventor Sana/Z12,

ie! 1W Patented Mar. 30, 1948 CONSTRUCTION OF RETRACTABLE LANDING GEARRaymond :Saulnier, Parla -France Application February 13, 1942, ."SerialIl\lo..430,621

,InFranee .May 15,1940

- SectionL-Public Law 690, Aug1i's't-8, 1946 Patent expires May-15,1960

15 Claims. ,1

The present invention relates to retractable landing gear .ofthe typeincludingza .shockabsorber which carries the .wheel,:pivoted to:.a'fixed point of the airplane structure)andimaintained in the landing orextended: position-by a 4 breakable. strut pivotedron the :onehand to. afixed point .of the airplane :and, :on :the other hand; 'to a point oftheshock absorber.

The invention relates .-.more aparti'cularly 1 to landing gear of thistype, in which the" point at which .the strut is pivoted Ito theusho-okabsorber is located closeito the lower endof the-cylinder of the shockabsorber, which-ensuresaa verygood resistance during landing.

More specifically, itheginvention relates to retractable landing gearjnwhichsthestrut is 'made of two portions :pivotedto .eachothersubstantially. at the middl'epoint ofxthestrut in such a manner that,when the :gear is in; the landing position-the p'ointof. articulationofthe-two portions of the 'strutis beyond thedead,center.:position, so as..to improve .safety. when landingyindependently of the locking of. the.strut.

According .to;.thev invention, the. folding pr .re-.

tractingv of the .landinggearnis. effected in two steps, the first .ofwhich consists, after. the. strut has been .re1eased,:in breakingdt.soasto cause, in the particularcasejust.abovementioned, the point ofarticulation'to passptoathe othergsideiof the dead center line,thesecond step-gbeinggperformed by the actionofa .jackjpivoted' on theone hand .to a' fixed :point; off i the airplane and, on the other:hand. .to the end of, a. lever rigid with the. sho,ck'-,absorber, so:as to cause :the :latterv to pivot: about the point at which it ismounted; on the. airplane.

One of :themostserious idifliculties which have to be .dealtwith inretractable landing gear, is to ensure a retraction of a gear with theminimum .of force, xwhich implies an efficientutilization. of.the-poweryof the retracting means.

An obj ect: ofzthe, present invention is vto .provide aretractingsdevice.suohthat the first step, which: starts the .breakingof :thestrut, and the second step which causes the shock absorber topivot about its-point of articulation onthe airplane, are :zproduce'dbya thrust'directedealong a line making ;an..-angle as small as possiblewith the optimum direction, accountabeing taken of the power to beexerted.

For this: purpose, according. to. afeature .of my invention; the strut.includes a system, of levers intended .to break thiss'strutand inparticular, to movetheu point; of articulation 'thereof :from one sidetoathe, other of the; deadcenter line.

, According-Qtoranother feature-of; the inven tion, the lifting {deviceproperi is arranged in such inannerthat the lever arm on whichthejack.is to act lengthens, during the lifting movement,

as ;;t he rresistance itself increases, whereby .the power requiredtoJoe-exerted by the jack never reachesyeryhigh values, since the ,forcerequiredtobie exerted at the end of the movement is rel atively.- small.

0ther -features of my inventionwill appear from the following detaileddescription .of some specific embodiments thereof.

Preferred embodiments of my invention .are

hereinafter, described, with reference to the .ac-

. shockabsorber which carries a wheel .W and-is pivoted ,at-H to a fixedpart M of the airplane. The shock absorber. :may be. maintained .or .notin ;its plane, .parallel .to the fore-and-aft ;plane ofv symmetry .of-v:the. airplane, *by a thrustbar,

. the latter ,being :pivoted .llOifl'lfiXGd part of the airplaneata.pointlocatedbehind point. H,..so thatathemhole can pivot about-alongitudinal axistpassingthrough these-two points. The landinggeargfurther includes a strutconstitutedby two portions A and A pivotedtoeach. other near the middle point of .the strut: at B. These twoportions: are, locked .in :the landing position .by a.locking.member-.C. whichis shown in a more detailedmanner byFig.i2.This'locking member isipreferably controlled pneumatically by a valve D.Y E and F. are thepoints where. thestrutis pivotedto:'the.-.airp1ane andto the shock absorber, respectively.

; The. retraction of .the landing gear. is. obtained lay-swinging .theshock absorber .G about :point absorber.

H, this movement being producedib'y the action ofa jack :V, one of whoseends. is pivoted to the airplane .-..-at a point J, while the other endvis pivoted .to a lever arm-I rigid with the shock Reference character:I designates: the operating. member, N. is :the compressed airinlet; K adistributer. for controllingthe. inflow ofoil under pressure and Q :a'vconduit through which oil 4 is fed to the-distributor. fDistributer Kisifurther 3 I connected through pipes K1 and K to the opposite ends ofjack V. Finally, valve D is connected through a pipe d to a pneumaticpiston P housed in strut A, A. V a

This device operates in the following manner: The first movement ofthe'operating lever T, in the direction of arrow f opens valve D, whichcauses compressed air to be fed into pipe d. Pneumatic piston P isactuated by this compressed air and pushes lever L, pivoted about anaxis 0, so as to move the locking member of the lever L (see Fig. 2),into inoperativeposition.

During the second part of this first movement, a projection R on lever Lstrikes a corresponding projection R of portion A of the strut, wherebyno risk of an accidental folding of the gear during landing; even tions,

Further,

under the most di-fiicult condireliable extension of the landing gear isassured by the gravity effect of the weight of the thrust of piston Pbreaks the strut just when the'two projections disengage from eachother. At this time, the movement of piston P is stopped by a'lug U.During this movement, the point B about which'the'two portions of thestrut are pivoted" to each other, passes from a position below lineE-'--F (where it was jammed in order to increase safety incase'ofnon-operation of the locking means) to the position B" on theother side of said line *E-F. The operating lever T is now at the endofits first movement in the direction of arrow 1 a a a The secondmovement of this operating lever T, in the direction of the arrow fpermits oil under-pressure to pass-through distributor K and throughconduit K into the near end of the jack V. This pushes lever I andcauses the shock absorber to' swing on its pivot H, whereby the landinggear isfullyfolded.

.Inithe embodiment which has just been described, the operating lever Tis given two successive movements, one serving to control the pneumaticpiston which starts the breaking of the strut, and the other operatingthe jack, whichfinishes the retroacting operation.

7 lnfthe'embodiment shown in Fig. 3, the pneumatic control valve D islocated between jack V and the point J of fixation thereof to theairplane. In this embodiment, the operation of the lifting deviceisfsimplified because only the flow of oil through the distributor Krequires to be controlled by the control element X.

' When the control lever X of Fig. 3 is moved, 1 oil" under pressure isfed through conduit K to the j'ack,.which tends to .push lever I, on theone hand; and'to open'v'alve D on the other hand. ,As'

lover I resists the thrust thus transmitted there- .the landing gear,the counter-pressure in the jack V, and the action of the elastic cableS,

which is stretched between the strut A, A and the frame M, t Anotheradvantage of the landing gear, ac-

V cording to the invention derives'from the fact that the powernecessary for retracting the gear is reducedto a minimum, As aboveexplained, the first movement, which starts the breaking of the strut,by unlocking it, necessitates only a very small force in view of theparticular ar- 7 rangement of the levers and the projections carried bythe parts of the strut. Furthermore, the

efiective leverageof the arm I, on which the lifting jack acts,increases as the force required ii creases, as above explained.

WhileI have, in the above description, dis-- closed what I deemto bepractical and eflicient:

embodiments of the present invention, it should? be well understoodthatI do notv wish to be lim--.

I ited thereto, as changes maybe made in the arrangement, dispositionand form of the parts,

without departing from the principle otthe pres-- ent invention, ascomprehended within the scope.-

of the appended claims. V

What I claim is:

r 1. A retractable landing gear including a shock absorber pivoted tothe airplane proper, a member adapted to run on the ground carried bysaid. shock absorber, a jointed strut pivoted at one end. to theairplane proper and at the other endto the shock absorber, saidstrut'being broken in,

the folded position of the landing gear and; straightened in theextended .position of said. landing gear, means for locking said strutin the: landing. position, means carried by the strut forbringing saidlocking means out of action and to, because stnitA-A is locked andtherefore cannot break, jack V compresses spring Y (see Fig. 4') andpermits valve D to be opened by the compressed air from the pipe N, sothat compressed air is passedto operate the piston P, so as to movelocking member 0 into inoperative position 'and'start the breaking ofthe strut in the manner explained above. The jack then bears against thepiece Z, provided in the Valve D for limiting its movement, and pusheson the lever I so as to retract the shock absorber.

i The landing gear according to the invention has many advantages, amongwhich the following may be cited: 1

, First, the safety obtained when landing is very high, since'the shockabsorber is well adapted to r resist transverse stresses, because it isbraced at a very low point by the strut. The strut cannot breakaccidentally since, even when it is not positively locked, said strut isbiased in the extended substantially simultaneously starting the breakfing of said strut, and a jack interposed between the airplane proper andsaid shock absorber for finishing'the folding movement started by theabove mentioned means.

. 2. A retractable landing gear including a shock absorber pivoted tothe airplane proper, a member adapted to much ,the ground carried bysaid shock absorben a jointed'strut'pivoted at one end to' the airplaneproper and at the other end to the shock absorber, said strut beingmadeof two parts pivoted to each otherat the middle point of thestrut'and being broken in the folded position of the landinggear andstraightened in the extended positionof said landing gear so that saidmiddle point passes slightly beyond the dead center line of the strut,means for locking said strut in the landing position, means carried bythe.

strut for bringing said'locking me'ans out ofaction and substantiallysimultaneously bringing above mentioned means T back said middle pointon 'the'other side of said dead center line, and a jack interposedbetween the airplane properiand said'shock absorber for finishing thefolding movement started by the 3. A'retractable landing gear ber'adapted'to run on the ground carried by said to the shock absorber,saidstrut being broken in the folded 'position, of the landing "gearan}?! including a shock 1 absorber pivoted to the airplane proper,a'memstraightened in "the ''i'ztzified position 'of said landing gear,sfir'ii i'g 'ii'iIn loklfig 'ali'd Strut in the mnmngposnmmpne ti'eariscarried by the strut for brii'i'g ifl g 'safd iockmgmeans out ofactionandsubstantiallly si-friiiltafri'ollsly starting the hi 'akingofsai'd fii'ii'tfa jack interposed between the airplane f'pro'pfand saidshock absorbr "fon'filiis'hihg 'the folding'l'ri'otem'ent started by'the abov mentioned means, and "means for feeding 'li'quid tinder 7pressure to Said jack.

4. A retractable l'l lfdifig'gafrih'ollidihgashock absorber "pivoted tothe""ei.irp1an'e :pr'eper, a membrada'ptedto when the ground-carried by'said shook "absorber, a jointed strut IliVOt'eH at one the foldedposition of the landing gear and straightened in the "iitlidd positionof said landing ge'arjspring ineansTorlo'ckingsaid strut in the landingposition, 'pneuinatic means carried by the strutforbrin'ging saidlookingmeans' out of action and substantially"simultaneously startingthe breaking "of said strut, a j efk interposed between'th e airplanepropfr and said shockacsorber for finishing the folding movement started'by the above i'ri'enti'on d 'in'e'ans, hydraulic means 'for feedingliquid under pressure to said jack, sndacommtn operating m'emb'erforsuccessively operating said pneuin'atic 'means and said hydraulic mean I5. A'retractab'le Ianuinggearinducin ashock absorber pivotedto'the"airplane"proper, 'a member "adapted to :run "on thegroundcarried bysaid shock absorber, "a 'joint'd "strut pivoted at one end to'theai'rpla'ne 1 proper "and *at' the other end to the shook "ibsblb'r,'saidjstrut being broken in the folded position "of the landing "gearand straightened in the extended position of said landing gear, springmeans "forlocking said strut in the landing position, pneumatic meanscarried by'thestrut'for bringing-said locking means out of action "andsubstantially simultaneously starting thebreaking of said st'rut; a jackinterposed betweenith'e airplane proper ena said shock absorber forfinishing the folding movement started by the above m'enti'dnedmeans;hydraulic means for feedin liquidunder pressure tosaid jack, "a 'lever'-a'dapted to be' given two different movements, means operated by saidlever for one of said movements foroperatingsaid pneumatic means andmeans "operated-by the loth'er movement of said lever 'for operating"said hydraulic means. i g I v 6. 'A retractable landing gear" includinga shock absorber pivoted to the *aii plane proper, a member adapted torun on thegrofind oarridbysaid shock absorber, a "jointed strut pivotedat one end to the airplane propenand-at the other end to the shock"absorber,"said'strutbeing broken in thefolded positionbfthe landinggear and straightened in the extended p'o'sition of said landing gear,spring means for locking said strut in the landing position, pneumaticmeans carried by the strut for bringing-{said locking irieans out ofaction and substari ally simultaneously starting the breaking of s'aidstrut, a jack" inter- 1 posed between the airplaneproper and said shockabsorber for finishing, When eXpandedQthe folding movementstartedbythe-above mentioned means, said jack having lost motion to give it aslight play at the beginning of its operation to complete t-he folding'in'oin'errient, hydraulic means for-feeding-lidu r'pressure to'saidjack, an a'ir valve for-conti'o Imgsaid 'pn'eumatic *nieans adapted tobe opend by the "expanding movement of said jack corresponding to thetakplane o'f the t'y'pe involviiig ariorinaily vertical 6 ing up of"said play, and valve means for "open atin'gsaid hydraulic'nieans.

7. A retractable "landing "gear facc'ordin'g to Claim "6 furtherincluding iever adapted to operate said last 'ni'e'n'tione'id valvemeans "in such manner that a first displacement-or said lever causes thejack totakeu'p its 'p'iayamim'ove mer t in the 'sam'ediretibh tiailse'ssaid 'jackto finish thefoldirig ofthe l'andinggear.

8. In a retractable-landing gearfor "airplanes, the combination of,"anelongated member pivoted at one end" to the-airplane owner and adaptedto swing from a downwardiyeiitendin position 'to a substantiallyfhorizontalflpbs'ition, "an "airplane supporting member carried u on thefree'end of said elongated memberga jack pivote'd 'at'one end to theairplane and'atitsotherend to the upper part of s'aid'elongated memberfor operating said elongated member into inoperative horizontalpositiona jointed'sti'utipivoted at one end to the airplane properan"dat the other to the elongated member'jand'bein'gmovablefrom a foldedposition in which saidelong'atedmember extends substantiallyhorizontally to an extended position in'whioh Saidelongated memberextends downwardly, 's aid strut comprising a" pair ofstrut membershaving a pivotal "connection which moves past thedeadcenter"of"the"strut when the strut approaches its'e'xtieiiteiitendefd position, Jatchmeans' on thestrutbrid'gi'ng said piv. otalconnection "so "as to il iold "sai d strut in its extended position,,"and fluid operated "rneans on the strut for operating said l'a tchmeans into inoperativepos'ition and for "mot/inten pivotal connectiontoward folded pastime-cites the dead center of thestrut, eas tobreak"theistrut.

v '9. In a retractable anuinggear for "an "airplane involving anelon'ga'tedfin'einberfhaving 'a round engaging element "at its lower endand 'Ineans at its upper "endfor' pivotal "connection with the airplaneto enable"said elongated membier to be retracted from as'libs'tantiallyvertical tudinal axes of said sections, said bre'akjointin. cluding a fixed joint element onfthe-l'owersection projectingalongside or "an"'a'djacent portion of the upper section emanating-a"camurface, said break joint further comprising-a," latch pivoted ontheupper section'hayihg"a"camf operatively 'engageable with the cams'u'rface whereby the lower" section is swu'rig away 'from the uppersection whenever said latch is in'ovedonitsp'ivot in one direction;saidlatch furtherhavin'g a detent portion latchable witha portion on thelower section when the sections are intheir extended positions, ahydraulic cylinderand'piston assembly mounted and operatinglongitudinallybn said upper section with a portion: of itspistonenga'geable with said cam to inove it in'sa'id one'direction-so as tosequentially disengage-said detent portion from latching relation to"thef lower section and swingsai'd lower s'ectionre ativ'e to-said uppersection thereby partiallyfolding 'the strut,

and hydraulic means 'for co'rfi-pletifigthe folding of the strut.

Y 10. In a retractable "landing gear rer enairof said elongated memberand an .joint swingably connecting. the sections, latch from said othersection with elongated member having a ground engaging ele-, ment at itslower end and'means for pivotingit at its upper end to an airplane,andafoldable strut extending between the lower part of saidelongatedmember and a part of the airplane, said strut comprisinganupp'er section pivoted at its upper end to the airplane and a lowersection pivoted at its lower end to the lower part off center breakmeans for locking the sections in extension of each other, said latchmeans comprising a cam pivoted on one section and a cam surface on theother section, a fluid cylinder and piston'assembly mountedlongitudinally on said one section, said ,piston being operatively'engageable with said'cam so asto move said cam against said cam surfaceso as to swing the sections relative to each other sufliciently to breakthe joint and permit the strut to move into folded position when saidassembly is operated, and means for completing the folding of thesections.

11. In a retractable landing gear for an airplane, a normally verticalshock-strut pivoted atrits upper end to the airplane,a foldable bracestrut extending between the lower part of the shock-strut and a part ofthe airplane remote from the pivotal point of the shock-strut, saidfoldable brace strut comprising upper and lower sections pivoted to theairplane and thelower part of the shock strut, respectively, and an, off

center break joint pivoting the ,sections together for folding relativeto each other and for substantial longitudinal alignment of the sectionsin their unfoldedposition, said break joint comprising a movable latchmember mounted on one of the sections andlockably engageable with theother section in the aligned relation of the 'sections, said latchmember having acam portion engageableafter release of the latch member aportion of said other section so as to move the latter so as to breakthe joint and impart preliminary movement of the sections relative toeach other toward ,folded position, said upper section having a hollowportion, and operating means comprising a fluid piston andicylinder insaid hollow portion and assembly mounted withlongitudinally with re-;spect to the uppersection and operatively en- ;gageable with saidmovable latch member.

12. In a retractable landing gear for an vairplane, the combination of alongitudinally acting shock absorber pivoted'at one end to the airplanefor swinging from a depending vertical operative position to asubstantially horizontal inoperative position, a groundrengaging elementon thefree end of said shock absorber, meansfor moving said shockabsorber into, and out of operative position, a foldable strutpivotedatone end to the airplane and at its other end .to the shock absorberadjacent toits said free end to brace the shock absorber inits'operative position, said foldable strut comprising a pair ofsections hinge means arranged ofi center on the sideof the strut remotefrom the shock absorberland hingedly connecting the sections togetherand permitting the sections to pivot-out of longitudinal alignment toenable the strut to fold toward the shock absorber as the shock absorberis swung upwardly from its vertical operative position toward itsinoperative horizontal position, the oil center location of thepivotalpoint of said-hinge means precluding the pivoting of saidsections out-of V longitudinal alignment in the opposite direction,latch means bridging and interconnecting the hinged ends of the strutsections for locking the sections when in longitudinal alignment, andcooperating means carried by'the adjacent ends of said strut sectionsfor'releasing said latch means and formovingth'esections past theiroil-center relation toward folded position to permit the sections topivot in a strut-folding operation.

13. In a retractable airplane landing gear, a longitudinally actingshock absorber pivoted at its upper end to the airplane to extenddownwardly in extended position'and havin a ground engaging element atits lower end, a foldable strut pivoted at its lower end to the lowerpart of said shock absorber and at its upper end to the airplane at apoint at one side of the pivotal point of the shock absorber, said strutcomprising a pair of sections, means hinging the sections together attheir inner ends to fold'toward the shock absorberas the landing gear isretracted to inoperative position and'to reach a position past deadcenter when restored to aligned position as the landing gear is extendedto operative position, locking means for locking the sections togetheras they move into their aligned position, a lever connected to the upperend of the shock absorber and turning on the pivot of the shockabsorber, a jack located at the strut side of the shock absorber andhaving one end connected to said lever and its opposite end to theairplane, and operating means for working the jack to retract and extendthe shock absorber, said operating means including means responsive tothe portion on said other of the )strut members to V latch the strutmembers, whereby the movement of the latch means towards inoperativeposition causes the cam elementto move the strut members relative toeachother and thereby break the strut. w

15, A retractable landing gear as described in claim 8 wherein said jackcomprises afiuid operated cylinder-piston unit and a valve mounted ononeend of the cylinder, said valve being responsive to the fluidpressure in said unit and controlling the supply of fluid to said fluidoperated means on the strut.

" I RAYMOND SA ULNIER.

, 1 REFERENCES CITED The following references are oflrecord in the fileof this patent:

' 'UNI'VI'ED STATESPATENTS Number Date Name 1,171,075 Taylor Feb, 8,1916 1,329,533 McCarrol Feb. 3, 1920 2,292,671 7 Sumner Aug. 11,1942

7 r V FOREIGN PATENTS Number Country 1 Date 464,144 Great Britain Apr.13, 1937 7 518,073 Great Britain Febjl6, 1940 7 518,130 Great BritainFeb, 19,1940

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